This invention relates to heat exchangers and more particularly to a device for scavenging condensate from inside long tubes of a heat exchanger.
When there are a number of tubes condensing in parallel, variations in condensing produces different flow patterns in different tubes, which result in condensate build-up in certain tubes. After the condensate plugs the tubes, the flooded tubes purge themselves and the cycle begins again resulting in thermal shock and stresses, which in time cause failure adjacent the area where the tubes are welded to the tube sheet.
One solution to this problem is to vent a portion of the steam to a lower pressure receptacle, increasing the flow through the tubes and thereby scavenging the condensate which collects in the tubes, however, unless very large quantities of steam are vented, this method is ineffective in keeping all the tubes free from plugs of condensate. From a thermodynamic standpoint, the greater the quantity of vented steam, the lower the thermal efficiency of the system and therefoe, the more costly it is to operate. Ritland et al in U.S. Pat. No. 3,759,319, issued Sept. 18, 1973, and assigned to the same assignee, describes one solution to this problem and this invention describes still another solution.